Method and arrangement for the traversing of the critical rotational speeds of elongate rotors

Abstract

A method and arrangement for the traversing of critical rotational speeds of elongate rotors. At least one critical frequency altering means in the form of springs, dampers and masses may be operatively connected, singly or in combination, to the rotor to thereby produce a change in the frequencies and/or amplitudes of the rotor, or in the critical rotational speeds and their amplitudes.

What is claimed is: 
     
       1. In a method for the traversing of the critical rotational speeds of elongate rotors, the improvement comprising alternately coupling in and uncoupling to said rotor at least one critical frequency altering means positioned substantially at an end of the elongate rotor, which is held by at least one stationary support member and encompasses but does not contact nor influence the rotor during noncritical running speeds of the rotor, directly responsive to radial rotor movement and due to variation in the flexural axis of the rotor upon approach of the rotor speed to the critical rotational speeds thereof, said critical frequency altering means being coupled to said rotor at a critical rotational speed and producing a change in at least the frequencies of the critical rotational speeds, their amplitudes, or the critical rotational speeds and their amplitudes. 
     
     
       2. A method as claimed in claim 1, said critical frequency altering means comprising at least one spring. 
     
     
       3. A method as claimed in claim 1, said critical frequency altering means comprising at least one damper. 
     
     
       4. A method as claimed in claim 1, said critical frequency altering means comprising at least one mass. 
     
     
       5. A method as claimed in claim 1, said critical frequency altering means comprising a combination of springs, dampers and masses. 
     
     
       6. A method as claimed in claim 1, comprising initiating activation and deactivation of said critical frequency altering means through the amplitude change of the rotor at the locations of flexural nodes. 
     
     
       7. A method as claimed in claim 1, comprising initiating activation and deactivation of said critical frequency altering means through the amplitude change at at least one end of said rotor. 
     
     
       8. A method as claimed in claim 1, said rotor being axially displaced by said amplitude change upon approaching a critical rotational speed, comprising coupling and uncoupling said critical frequency altering means to and from said rotor responsive to the axial displacement of the latter. 
     
     
       9. A method as claimed in claim 1, comprising withdrawing energy from said rotor through a damper upon contact with said critical frequency altering means. 
     
     
       10. A method as claimed in claim 1, one portion of the rotor initially increasing in rigidity with increasing amplitude and suddenly assuming another or original rigidity value. 
     
     
       11. A method as claimed in claim 1, one portion of the rotor initially decreasing in rigidity with increasing amplitude and suddenly assuming another or original rigidity value. 
     
     
       12. In an arrangement for the stabilizing of an elongate rotor by traversing the critical rotational speeds thereof, the improvement of critical frequency altering means held by at least one stationary support member and arranged coaxially with and at predetermined close spacing to a portion of said rotor substantially at an end thereof in a noncontacting and noninfluencing manner at noncritical rotational speeds, said traversing aid means being directly coupled to and uncoupled from said rotor responsive to amplitude increases of said rotor, said critical frequency altering means being coupled to said rotor at a critical rotational speed and producing a change in at least the frequencies of the critical rotational speeds, their amplitudes, or the critical rotational speeds and their amplitudes. 
     
     
       13. An arrangement as claimed in claim 12, said critical frequency altering means means comprising at least one spring. 
     
     
       14. An arrangement as claimed in claim 12, said critical frequency altering means comprising at least one damper. 
     
     
       15. An arrangement as claimed in claim 12, said critical frequency altering means comprising at least one mass. 
     
     
       16. An arrangement as claimed in claim 12, said critical frequency altering means comprising a combination of springs, dampers and masses. 
     
     
       17. An arrangement as claimed in claim 12, said critical frequency altering means engaging said rotor radially thereof. 
     
     
       18. An arrangement as claimed in claim 12, comprising means for regulating the rigidity, mass or extent of damping of said critical frequency altering means responsive to the rotational speed of said rotor. 
     
     
       19. An arrangement as claimed in claim 18, said regulating means comprising means for producing magnetic coupling forces. 
     
     
       20. An arrangement as claimed in claim 12, said critical frequency altering means being adapted to auxiliary drive said rotor during acceleration of the latter and brake said rotor during deceleration thereof. 
     
     
       21. An arrangement as claimed in claim 12, said critical frequency altering means engaging said rotor. 
     
     
       22. An arrangement as claimed in claim 12, said critical frequency altering means comprising means encompassing said rotor with predetermined play therebetween; and resilient means fastened to a stationary frame rotatably supporting said means but not being rotatable therewith. 
     
     
       23. An arrangement as claimed in claim 22, said encompassing means comprising a ring. 
     
     
       24. Arrangement as claimed in claim 22, said rotor-encompassing means including a conical contact surface; a complementary member on said rotor engaging in said conical surface upon said rotor displacing in an axial direction when approaching a critical rotational speed. 
     
     
       25. Arrangement as claimed in claim 22, said rotor-encompassing means being driven in an uncoupled condition intermediate the critical rotational speeds of the rotor at a corresponding speed so as to accelerate said rotor upon contact therewith and to retard the rotor during deceleration. 
     
     
       26. Arrangement as claimed in claim 12, said encompassing means comprising a plurality of dampingly and resiliently supported rollers uniformly arranged about said rotor. 
     
     
       27. Arrangement as claimed in claim 12, said rotor including a needle-like projection, said critical frequency altering means comprising a hollow cylinder encompassing said projection, said hollow cylinder having an inner diameter reducing towards the free end of said projection. 
     
     
       28. Arrangement as claimed in claim 12, said critical frequency means being arranged interiorly of said rotor. 
     
     
       29. Arrangement as claimed in claim 28, said critical frequency altering means having its rigidity changed interiorly of said rotor so as to influence the frequencies and amplitudes of said rotor during traversing of critical rotational speeds in a predetermined direction. 
     
     
       30. Arrangement as claimed in claim 28, said critical frequency altering means comprising a damping chain, and means for changing the rigidity of said chain through varying of pulling forces in the axial direction of said chain. 
     
     
       31. Arrangement as claimed in claim 12, comprising a plurality of said critical frequency altering aid means being spaced along the length of said rotor. 
     
     
       32. Arrangement as claimed in claim 31, said critical frequency altering means being located at the oscillation nodes of said rotor.